In recent years there has been a great deal of effort directed to the development of sulfonamides having herbicidal activity, and several of these compounds have reached the stage of commercialization, i.e., chlorosulfuron and sulfometuron methyl. These compounds exhibit both preemergence and postemergence activity against undesirable vegetation and, in addition, have a low toxicity to mammals. The compounds of the prior art may be depicted as follows: ##STR1## wherein Ar is usually a benzene derivative and Ar' is usually a pyrimidine or symmetrical triazine derivative.